Fears are growing for the future of the semi-feral ponies that wander Dartmoor following a poor sale of young stock.

Numbers are down and prices depressed, raising fears among campaigners for the horses that the ancient practice of farmers grazing them on the moorland may soon be at an end.

Some foals at the recent Chagford horse market failed to attract buyers, even at prices as low as £10.

The depressed market is a concern for the semi-feral herds across Britain, as unless there is a market for the young stock there is little incentive for farmers to maintain the practice.

The ponies are important in maintaining the careful ecological balance on the moorland. Without them, the moorland would become overgrown. They also are a popular tourist attraction.

The Friends of the Dartmoor Hill Pony, a registered charity, has introduced several measures in recent years to reduce foal numbers, while keeping the ponies on the moor.

These include gelding stallions, using long-term contraceptives in mares and the removal of stallions from enclosed commons.

However, some young stock has gone unsold in the drift sales this year, and one report has suggested some animals may ultimately go to slaughter.

The number of Dartmoor Hill ponies has fallen from about 30,000 in the 1950s to about 850 today. They have been on the moor for more than 3000 years.

The charity says: “The economic downturn has meant many foals are not selling at the annual drift sales and without this income for the pony keepers the practice of breeding these semi-feral hill ponies could stop.

Dartmoor ponies from the Norfolk Wildlife Trust’s herd.

“That would not only be a disaster for tourism – but also for maintaining the unique ecosystem on Dartmoor; it’s the selective grazing style of the ponies that benefits invertebrates, mammals and birds alike. Without them, Dartmoor as we know it cannot be maintained.”

Officially, a Dartmoor Hill Pony is a pony that has been bred on the commons of Dartmoor, by a registered commoner, and whose sire and dam run on the commons.

They all look different and there are many varieties of colour and type, but they all have the same underlying tradition of hardiness and the majority a good temperament, the charity says.

In autumn, the ponies are herded off the commons down on to the farms.

The commoners check their herds, and the foals are weaned from their mothers and sent to the local pony sales.

The mares are let out again and return to the commons.

Any revenue from the ponies that are sold hopefully goes toward the cost of keeping the rest of the herd.